Perfluorocompound-specific enrichment element, method for preparing the same, and use thereof

Abstract

This invention discloses a perfluorinated compound-specific enrichment element, its preparation method, and its applications. The method for preparing the enrichment element includes: providing a non-metallic base rod; adhering graphene oxide powder to a portion of the surface of the base rod to obtain a preliminary enrichment element; contacting the preliminary enrichment element, template molecules, functional monomers, and a porogen to conduct a prepolymerization reaction to obtain a prepolymerized mixture; adding a crosslinking agent and an initiator to the prepolymerized mixture, mixing, and then conducting a polymerization reaction under vacuum to obtain an enrichment element intermediate; and eluting the enrichment element intermediate to obtain the enrichment element. The enrichment element prepared by this method has a uniform coating, good specificity for the adsorption and enrichment of perfluorinated compounds, and strong adsorption force. Furthermore, the eluent of the enrichment element can be used for detection by liquid chromatography or as a stationary substrate for mass spectrometry detection via ionization.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, and more specifically, to perfluorinated compound specific enrichment elements, their preparation methods, and applications. Background Technology

[0002] Perfluorinated compounds (PFCs) possess hydrophobic / lipophobic properties and are chemically and thermally stable, making them widely used in industrial and consumer products, including fire-extinguishing foam materials, food packaging, water-resistant and non-stick textiles, and non-stick cookware linings. Considering the persistence of PFCs and their degradation products, as well as the increasing production and usage, PFCs remaining in the environment will eventually accumulate through the food chain, posing toxic hazards to humans. Studies have shown that long-term exposure to PFCs can lead to reproductive and nervous system disorders in men, and endocrine, immune, and reproductive system defects in women. Therefore, the detection of trace PFCs in the environment and food is particularly important. Currently, the main methods for PFC detection include gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography-mass spectrometry (HPLC-MS), and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS / MS). However, the detection using GC-MS / MS is time-consuming and requires complex pretreatment processes such as extraction, purification, and enrichment.

[0003] To avoid complex pretreatment processes, researchers have begun to consider developing different adsorbent materials for the extraction and enrichment of target analytes in samples. Suwannakot et al. prepared metal-organic frameworks (MOFs) to extract PFOA from environmental water samples. Cao et al. prepared a surface molecularly imprinted polymer based on multi-walled carbon nanotubes, which can be used for the adsorption and removal of PFOA in the aquatic environment. However, these materials are difficult to use with subsequent mass spectrometry instruments. The adsorbent materials lack selectivity or have poor selectivity, making it impossible to enrich and separate trace or even ultra-trace levels of perfluorinated compounds in complex matrices. This results in significant matrix effects, high instrument detection limits, and difficulty in achieving accurate determination of trace substances.

[0004] Therefore, the technology for enriching and detecting perfluorinated compounds needs to be improved. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide an enrichment element that can specifically adsorb perfluorinated compounds, and that the enrichment element is suitable for detection by analytical methods such as chromatography-tandem mass spectrometry, open solid-substrate electrospray mass spectrometry, etc., and is particularly suitable for the enrichment and detection of perfluorinated compounds in environmental samples and complex food matrix samples.

[0006] According to one aspect of the present invention, a method for preparing enriched elements is provided. According to an embodiment of the present invention, the method includes: providing a non-metallic substrate rod; adhering graphene oxide powder to a portion of the surface of the substrate rod to obtain a preliminary enriched element; contacting the preliminary enriched element, template molecules, functional monomers, and a porogen with a prepolymerization reaction to obtain a prepolymerized mixture; adding a crosslinking agent and an initiator to the prepolymerized mixture, mixing, and then performing a polymerization reaction under deoxygenated conditions to obtain an enriched element intermediate; and eluting the enriched element intermediate to obtain the enriched element.

[0007] According to the method for preparing enrichment elements in the embodiments of the present invention, the enrichment element coating is uniform, has good specificity for the adsorption and enrichment of perfluorinated compounds, and has strong adsorption force. Furthermore, the eluent of the enrichment element can be used for detection by liquid chromatography or as a stationary substrate for mass spectrometry detection by ionization. The detection steps are simple and the background noise of the detection is low, making it particularly suitable for the enrichment and detection of perfluorinated compounds in environmental samples and complex food matrix samples.

[0008] In addition, the method for preparing enriched elements according to the above embodiments of the present invention may also have the following additional technical features:

[0009] According to an embodiment of the present invention, the template molecule is a perfluorinated compound, preferably perfluorooctanoic acid (PFOA).

[0010] According to an embodiment of the present invention, the functional monomer is acrylamide (AAM).

[0011] According to an embodiment of the present invention, the crosslinking agent is ethylene glycol dimethacrylate (EGDMA).

[0012] According to an embodiment of the present invention, the molar ratio of the template molecule to the monomer and the crosslinking agent is 1:5-8:10-20.

[0013] According to an embodiment of the present invention, the initiator is azobisisobutyronitrile (AIBN).

[0014] According to an embodiment of the present invention, the porogen is acetonitrile.

[0015] According to an embodiment of the present invention, the base rod is made of wood or bamboo.

[0016] According to an embodiment of the present invention, the base rod has a tapered tip.

[0017] According to an embodiment of the present invention, the diameter of the base rod is not greater than 15 mm, and the diameter of the tapered tip of the base rod is not greater than 0.25 mm.

[0018] According to an embodiment of the present invention, the prepolymerization reaction is carried out under shaking conditions for 1-2 hours.

[0019] According to an embodiment of the present invention, the polymerization reaction is carried out at a temperature of 60-70°C for 20-30 hours, preferably 24 hours.

[0020] According to an embodiment of the present invention, prior to the prepolymerization reaction, the process further includes: subjecting the initial element product to ultrasonic cleaning with methanol and nitrogen blowing drying to obtain a dry enriched initial element product.

[0021] According to an embodiment of the present invention, the method includes: polishing the base rod until smooth, immersing it in a methanol solution for ultrasonic cleaning, and drying it with nitrogen to obtain a pretreated base rod; coating a portion of the surface of the pretreated base rod with a neutral silicone adhesive solution, adhering the graphene oxide powder to the base rod, drying it at 40-60°C, ultrasonically cleaning it with methanol, and drying it with nitrogen to obtain the initial enrichment element; adding the initial enrichment element, template molecules, and the functional monomer to the porogen, placing it on a shaker, and carrying out the prepolymerization reaction for 1-2 hours at 250-350 rpm and room temperature; adding the crosslinking agent and the initiator, purging with nitrogen to remove oxygen, and carrying out the polymerization reaction for 20-24 hours under sealed conditions at 62-68°C to obtain the semi-finished enrichment element; and eluting the semi-finished enrichment element in a Soxhlet enricher with a methanol solution containing 8-12% acetic acid to obtain the enrichment element.

[0022] According to another aspect of the present invention, an enrichment element is provided. According to an embodiment of the present invention, the enrichment element is prepared using the aforementioned method for preparing an enrichment element. Thus, the enrichment element of the present invention has a uniform coating, good specificity for the adsorption and enrichment of perfluorinated compounds, strong adsorption force, and the eluent of the enrichment element can be used for detection by liquid chromatography or as a stationary substrate for mass spectrometry detection by ionization. The detection procedure is simple, and the background noise is low, making it particularly suitable for the enrichment and detection of perfluorinated compounds in environmental samples and complex food matrix samples.

[0023] According to another aspect of the present invention, a detection device is provided. According to an embodiment of the present invention, the detection device includes the aforementioned enrichment element. The detection device of the present invention utilizes the high specificity and strong adsorption force of the aforementioned enrichment element for the adsorption and enrichment of perfluorinated compounds. Furthermore, the eluent of the enrichment element can be used for detection by liquid chromatography or as a stationary substrate for mass spectrometry detection by ionization. The detection procedure is simple, and the background noise is low, making it particularly suitable for the enrichment and detection of perfluorinated compounds in environmental samples and complex food matrix samples.

[0024] According to another aspect of the present invention, a method for qualitative / quantitative detection of perfluorinated compounds is provided. According to embodiments of the present invention, the method is performed using the aforementioned enrichment element or the aforementioned detection device. Therefore, the enrichment exhibits good specificity, strong adsorption, and fast adsorption rate, making it particularly suitable for the enrichment and detection of perfluorinated compounds in environmental samples and complex food matrix samples.

[0025] According to embodiments of the present invention, the perfluorinated compound is perfluorooctanoic acid (PFOA) or perfluorooctane sulfonic acid (PFOS).

[0026] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0027] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0028] Figure 1 A schematic diagram showing the preparation process of an enrichment element for enriching trace perfluorinated compounds according to an embodiment of the present invention is provided.

[0029] Figure 2 The diagram shows a scanning electron microscope (SEM) image of an enriched element according to an embodiment of the present invention, wherein A is an SEM image of the enriched element at 30 magnification; B is an SEM image of NIGOWT at 1.0K magnification; C is an SEM image of NIGOWT at 2.0K magnification; D is an SEM image of MIGOWT at 1.0K magnification; and E is an SEM image of MIGOWT at 2.0K magnification.

[0030] Figure 3 The diagram shows the selective and competitive extraction capabilities of the enrichment elements prepared using the methods of Example 1 and Comparative Example 1 for four perfluorinated compounds, where A is a schematic diagram of selective extraction capability and B is a schematic diagram of competitive extraction capability.

[0031] Figure 4 A schematic diagram illustrating the reusability of an enrichment element according to an embodiment of the present invention is shown. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0033] In the description of this invention, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and do not require that this invention must be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0034] According to one aspect of the present invention, a method for preparing enrichment elements is provided. The enrichment elements prepared according to the embodiments of the present invention exhibit good specificity and strong adsorption capacity for the adsorption and enrichment of perfluorinated compounds. Furthermore, the eluent of the enrichment elements can be used for detection by liquid chromatography or as a stationary substrate for mass spectrometry detection via ionization. The detection steps are simple, and the background noise is low, making it particularly suitable for the enrichment and detection of perfluorinated compounds in environmental samples and complex food matrix samples.

[0035] To facilitate understanding of the method for preparing enriched elements according to embodiments of the present invention, the method is explained and described herein, as follows:

[0036] S100 provides base rod

[0037] According to an embodiment of the present invention, a non-metallic base rod is provided. Thus, using the base rod as a carrier covered with adsorbent material facilitates the adsorption process.

[0038] According to an embodiment of the present invention, the base rod is processed from wood or bamboo. Therefore, the microstructure of the base rod surface is porous, facilitating cross-linking polymer coating and resulting in a functional material layer with a large specific surface area.

[0039] According to an embodiment of the present invention, the diameter of the substrate rod is no greater than 15 mm. According to an embodiment of the present invention, the substrate rod has a tapered tip, that is, the substrate rod has a pointed shape in its top view. Further, according to an embodiment of the present invention, the diameter of the tapered tip of the substrate rod is no greater than 0.25 mm. This facilitates open-type solid-substrate electrospray mass spectrometry analysis. The enrichment element is fixed at the horizontal front end of the mass spectrometer inlet. By applying a spray solvent, the target analyte adsorbed on the surface of the substrate rod can be eluted, and through the action of a high-voltage power supply, it is ionized at the tip to form a Taylor cone spray, which directly enters the mass spectrometer for detection. At this size, the efficiency of solvent elution and spray formation is higher.

[0040] It should be noted that when the tip of the base rod is placed vertically downwards, the projection onto the horizontal plane, the term "radius" used in this invention refers to the diameter of the smallest circle that can cover the projection. The diameter of the base rod refers to the vertical projection of the entire base rod, while the diameter of the conical tip refers to the projection of the conical tip.

[0041] S200 prepares initial components

[0042] According to an embodiment of the present invention, graphene oxide powder is adhered to a portion of the surface of the substrate rod to obtain a preliminary enrichment element. The inventors discovered that when using wooden or bamboo rods as substrate rods for open-substrate electrospray mass spectrometry analysis, the poor conductivity of the wooden or bamboo rods results in high background interference after applying high voltage, leading to unstable mass spectrometry signals. However, with graphene oxide-modified substrate rods, due to the conductivity of graphene oxide, high voltage can be directly applied to the substrate rod, resulting in high ionization efficiency and further simplifying experimental procedures.

[0043] According to an embodiment of the present invention, graphene oxide powder is adhered to a portion of the surface of the base rod using silicone adhesive. This results in good adhesion.

[0044] According to an embodiment of the present invention, the pretreated base rod is vertically inserted into a silicone adhesive solution and held for 30 seconds. The base rod is then immediately inserted into graphene oxide powder and held for 60 seconds. The base rod with graphene oxide adhering to its surface is removed and placed in a constant temperature drying oven, where it is dried at 50°C for 2 hours. Then, the graphene oxide-modified base rod is ultrasonically cleaned with methanol for 60 seconds and dried with a nitrogen stream to obtain the graphene oxide-modified base rod.

[0045] S300 prepolymerization reaction

[0046] According to an embodiment of the present invention, the enrichment element precursor, template molecule, functional monomer, and porogen are contacted to undergo a prepolymerization reaction to obtain a prepolymerized mixture system, ensuring sufficient contact between the template molecule and the functional monomer. This facilitates subsequent polymerization reactions.

[0047] According to an embodiment of the present invention, the prepolymerization reaction is carried out under shaking conditions for 1-2 hours. This facilitates the full progress of the prepolymerization reaction.

[0048] S400 polymerization reaction

[0049] According to an embodiment of the present invention, a crosslinking agent and an initiator are added to the prepolymerized mixture, and the mixture is then subjected to a polymerization reaction under deoxygenation conditions to obtain an enrichment element intermediate. Thus, the prepolymerized base rod is polymerized with the crosslinking agent to obtain a crosslinked polymer incorporating the compound to be enriched, thereby forming pores that match the spatial configuration and chemical bonds of the compound to be enriched, facilitating the entry of template molecules and their analogues into these pores during subsequent enrichment processes.

[0050] According to embodiments of the present invention, the template molecule is a perfluorinated compound, preferably perfluorooctanoic acid (PFOA). PFOA is persistent, bioaccumulative, and toxic, causing serious and irreversible effects on the environment and human health, and is one of the representative perfluorinated compounds.

[0051] According to an embodiment of the present invention, the functional monomer is acrylamide (AAM). AAM contains polymerizable double bonds and has functional groups capable of specifically recognizing perfluorinated template molecules to form a reversible complex.

[0052] According to an embodiment of the present invention, the crosslinking agent is ethylene glycol dimethacrylate (EGDMA). Therefore, the crosslinking reaction between ethylene glycol diacrylamide ester and acrylamide is highly efficient, the reaction conditions are mild, and the raw materials are inexpensive, readily available, and the resulting polymer has stable chemical properties.

[0053] According to an embodiment of the present invention, the molar ratio of the template molecule to the monomer and the crosslinking agent is 1:5-8:10-20. Therefore, the proportion of functional monomer grafted onto the crosslinking agent is appropriate, effectively initiating the crosslinking polymerization reaction, and resulting in a molecularly imprinted layer with good imprinting effect.

[0054] According to an embodiment of the present invention, the initiator is azobisisobutyronitrile (AIBN). According to an embodiment of the present invention, the porogen is acetonitrile. Thus, the initiator azobisisobutyronitrile (AIBN) can efficiently catalyze the crosslinking reaction, while when the porogen is acetonitrile, it can effectively promote the formation of three-dimensional pores in the crosslinked material that match the molecular size and shape, accommodating the test compound.

[0055] According to an embodiment of the present invention, the polymerization reaction is carried out at a temperature of 60-70°C for 20-30 hours, preferably 24 hours. This facilitates the full progress of the polymerization reaction.

[0056] According to an embodiment of the present invention, prior to the prepolymerization reaction, the process further includes: ultrasonically cleaning the initial element sample with methanol to remove residual template molecules, monomers, crosslinking agents and pore-forming agents, followed by nitrogen blowing drying to obtain a dry enriched initial element sample.

[0057] S500 elution process

[0058] According to an embodiment of the present invention, the enriched element intermediate is eluted to obtain the enriched element. This removes the template molecules embedded in the crosslinked polymer, thus forming a coating with specific pores, thereby obtaining the enriched element.

[0059] According to an embodiment of the present invention, the enrichment element semi-finished product is placed in a Soxhlet extractor and eluted with an eluent. Specifically, the eluent is a mixture of methanol and acetic acid, preferably a methanol solution containing 8-12% acetic acid. This provides good elution of template molecules such as perfluorooctanoic acid, which is beneficial for thoroughly removing template molecules from the pores.

[0060] According to an embodiment of the present invention, the elution process is carried out in a Soxhlet extractor, followed by washing with methanol until neutral, drying, and storage for later use. This facilitates the thorough removal of the compounds to be enriched from the crosslinked polymers.

[0061] To facilitate understanding of the method for preparing enriched elements according to embodiments of the present invention, a general method for preparing enriched elements is provided herein. According to an embodiment of the present invention, the method includes:

[0062] After the base rod is polished smooth, it is immersed in methanol solution for ultrasonic cleaning and then dried with nitrogen gas to obtain a pretreated base rod.

[0063] A portion of the pretreated base rod is coated with a neutral silicone adhesive solution, and the graphene oxide powder is adhered to the base rod. The rod is then dried at 40-60°C, ultrasonically cleaned with methanol, and dried with nitrogen to obtain the initial enrichment element.

[0064] The enrichment element, template molecule, and functional monomer are added to the porogen and placed on a shaker. The prepolymerization reaction is carried out at 250-350 rpm and room temperature for 1-2 hours. The crosslinking agent and the initiator are added, nitrogen is blown to remove oxygen, and the polymerization reaction is carried out under sealed conditions at 62-68℃ for 20-24 hours to obtain the enrichment element semi-finished product.

[0065] The enriched element semi-finished product is eluted in a Soxhlet extractor with a methanol solution containing 8-12% acetic acid to obtain the enriched element.

[0066] According to another aspect of the present invention, an enrichment element is provided. According to an embodiment of the present invention, the enrichment element is prepared using the aforementioned method for preparing an enrichment element. Therefore, the enrichment element of the present invention exhibits good specificity and strong adsorption capacity for the adsorption and enrichment of perfluorinated compounds. Furthermore, the eluent of the enrichment element can be used for detection by liquid chromatography or as a stationary substrate for mass spectrometry detection via ionization. The detection procedure is simple, and the background noise is low, making it particularly suitable for the enrichment and detection of perfluorinated compounds in environmental samples and complex food matrix samples.

[0067] According to another aspect of the present invention, a detection device is provided. According to an embodiment of the present invention, the detection device includes the aforementioned enrichment element. The detection device of the present invention utilizes the high specificity and strong adsorption force of the aforementioned enrichment element for the adsorption and enrichment of perfluorinated compounds. Furthermore, the eluent of the enrichment element can be used for detection by liquid chromatography or as a stationary substrate for mass spectrometry detection by ionization. The detection procedure is simple, and the background noise is low, making it particularly suitable for the enrichment and detection of perfluorinated compounds in environmental samples and complex food matrix samples.

[0068] According to an embodiment of the present invention, the perfluorinated compound is perfluorooctanoic acid (PFOA) or perfluorooctane sulfonic acid (PFOS). (In describing the features of the dependent claims, one example according to the present invention is used; when the dependent claims are further defined to include a feature, another embodiment according to the present invention may be used.)

[0069] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and should not be construed as limiting the present invention.

[0070] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products, such as those purchased from Sigma.

[0071] The materials and reagents used in the embodiments of this invention are shown in Table 1.

[0072] Table 1

[0073]

[0074] Example 1

[0075] Using the method of this invention, an enrichment element is prepared using perfluorooctanoic acid (PFOA) as the compound to be enriched, as detailed below:

[0076] A smooth, uniform wooden tip (Φ3mm) was selected as the base rod. It was sanded and cleaned with methanol to remove surface contaminants, which improves the adhesion between the silicone adhesive solution and the wooden tip. The tip was then dried with nitrogen and stored for later experiments. The base rod was vertically inserted into the silicone adhesive solution for 30 seconds, then immediately inserted into a test tube containing some graphene oxide powder for 60 seconds. The graphene oxide-coated base rod was removed and placed in a constant temperature drying oven at 50℃ for 2 hours. The graphene oxide-modified wooden tip (GOWT) was then ultrasonically cleaned with methanol for 60 seconds, dried with nitrogen, and the tip was uniformly cut to a length of 2.0 cm using scissors and stored for later experiments.

[0077] 50 mL of acetonitrile, 1 mmol of perfluorooctanoic acid (PFOA) as the compound to be enriched, 6 mmol of acrylamide (AAM) as the functional monomer, and GOWT were added to a round-bottom flask. The flask was placed on a shaker and prepolymerized at 300 rpm and room temperature for 2 hours. Then, 12 mmol of EGDMA and 100 mg of AIBN were added as crosslinking agents and initiators, respectively. The mixture was ultrasonically mixed for 2 minutes, purged with nitrogen for 10 minutes, and the round-bottom flask was sealed and evacuated. Finally, the flask was placed on a thermostatic magnetic stirrer and polymerized at 65 °C for 24 hours. After the polymerization reaction, the rod was ultrasonically cleaned in methanol for 5 minutes and then repeatedly eluted with a methanol:acetic acid solution (9:1, v / v) in a Soxhlet extractor to remove the compound to be enriched. After elution of the compound to be enriched, the rod was washed with methanol until neutral and dried to obtain a molecularly imprinted graphene oxide coated woodentip (MIGOWT).

[0078] Comparative Example 1

[0079] The enriched element (NIGOWT) was prepared using the method described in Example 1, except that perfluorooctanoic acid (PFOA) was not added.

[0080] Example 2

[0081] In this embodiment, the enriched elements prepared in Example 1 and Comparative Example 1 are characterized as follows:

[0082] The microstructure of MIGOCS was characterized using a scanning electron microscope (S4800) at an accelerating potential of 10 kV. The scanning results are shown in Figure 2. The experimental results show that the polymer-imprinted coating on the graphene oxide surface is uniformly adhered to the surface of the wooden stick. Figure 2 A); As in Comparative Example 1, when no template molecule is added, the functional monomers and crosslinking agents combine freely, and the microstructure shows that the polymer is connected in sheets to form a blocky structure. Figure 2 B, C); As in Example 1, when template molecules are added, monomers and template molecules bind to each other through hydrogen bonds during the prepolymerization stage. Subsequently added crosslinking agents encapsulate the template molecules and connect them to the monomers, forming a porous structure with recognition cavities. Electron microscopy characterization reveals a more detailed crosslinked framework structure. MIPs exhibit a denser and rougher surface than NIPs, providing a structural basis for the selective adsorption and rapid desorption of trace target analytes. Figure 2 D, E).

[0083] Figure 2 The diagram shows a scanning electron microscope (SEM) image of an enriched element according to an embodiment of the present invention, wherein A is an SEM image of the enriched element at 30 magnification; B is an SEM image of NIGOWT at 1.0K magnification; C is an SEM image of NIGOWT at 2.0K magnification; D is an SEM image of MIGOWT at 1.0K magnification; and E is an SEM image of MIGOWT at 2.0K magnification.

[0084] Example 3

[0085] In this embodiment, the enrichment elements of Example 1 and Comparative Example 1 are used to enrich the perfluorinated compounds in the test samples, as detailed below:

[0086] 1) Competitive adsorption experiment

[0087] Standard solutions of PFOA, PFOS, PFBA, and PFBS, as well as a mixed standard solution of the four substances, were prepared at a concentration of 50 ng / mL. The adsorption capacities of MIGOWT and NIGOWT for PFOA, PFOS, and structurally similar PFBA and PFBS were investigated using selective and competitive adsorption methods. All enrichment processes were performed at room temperature, with extraction under vortexing at 160 rpm for 25 min. After extraction, the enrichment elements were rapidly washed with deionized water for 10 s to remove surface impurities, ready for subsequent experiments.

[0088] 2) Detection and Analysis

[0089] Direct detection and analysis of the enrichment element was performed using open-substrate electrospray ionization mass spectrometry. The detection conditions included: the MIGOWT was fixedly mounted on a three-dimensional moving platform, with the enrichment element tip horizontally pointing towards the MS inlet, and adjusted to a position 5 mm from the MS inlet. Methanol was continuously supplied as the eluent at a rate of 5 μL / min using a controllable microflow pump. A high-voltage power supply was moved to apply a -4.25 kV high voltage through a copper clamp to the enrichment element, causing the target analyte to be spray-ionized at the enrichment element tip and enter the mass spectrometer for analysis. To validate the MIGOWT-ESI-MS method, target analysis was performed using an AB SCIEX QTRAP 5500 ion trap mass spectrometer in negative ion mode and MRM mode.

[0090] 3) Experimental Results

[0091] The enrichment elements of Example 1 and Comparative Example 1 were used to selectively evaluate four perfluorinated compounds (PFOA, PFOS, PFBA, and PFBS). A plot of the ion peak area of ​​the target analyte was created, and the results are shown below. Figure 3 The results show that MIGOWT exhibits stronger adsorption capacity for PFOA and PFOS than NIGOWT. Competitive adsorption in the mixed solution reduced the adsorption capacity of MIGOWT for PFOA and PFOS by 11.3% and 14.7%, respectively, compared to single adsorption, but it was still higher than that of NIGOWT. PFBA and PFBS, due to their short-chain structures and significant structural differences from the template molecule, showed poor selective adsorption. The experimental results demonstrate that MIGOWT possesses selective adsorption sites, indicating that the enrichment element in Example 1 exhibits unique selectivity for PFOA and PFOS.

[0092] Example 4

[0093] In this embodiment, the enrichment elements of Example 1 were used to enrich and detect PFOA and PFOS in spiked environmental water samples and milk samples, as detailed below:

[0094] 1) Experimental methods

[0095] River water samples used in the experiment required no pretreatment and were stored at 4℃ for subsequent experiments. For milk samples, a blank milk matrix was prepared using a simple protein precipitation pretreatment. 10.0 mL of milk was accurately weighed and added to a 50 mL polypropylene centrifuge tube, along with 20.0 mL of acetonitrile. The mixture was vortexed at 1200 rpm for 10 min using a multi-tube vortex mixer, followed by centrifugation at 9000 rpm and 4℃ for 5 min using a high-speed refrigerated centrifuge. 10 mL of the supernatant was accurately collected, dried using a smart nitrogen blower, and 5 mL of deionized water was added to dissolve the residue. Several blank milk matrices were prepared and stored at 4℃ for subsequent experiments. To assess the recovery rate, PFOA and PFOS at concentrations of 5, 10, and 50 ng / mL were added to the water and milk samples. Open-system solid-substrate electrospray ionization mass spectrometry was used for direct detection and analysis of the enriched elements.

[0096] 2) Experimental Results

[0097] The recoveries of PFOA in environmental water samples and milk samples were 86.5–112.7% and 82.3–104.1%, respectively, with RSDs of 3.96–8.79% and 4.24–8.83%, respectively. The recoveries of PFOS in environmental water samples and milk samples were 83.1–107.2% and 82.8–109.5%, respectively, with RSDs of 2.76–8.95% and 2.42–9.54%, respectively. These results indicate that the prepared MIGOWT can achieve good recoveries of trace amounts of PFOA and PFOS present in environmental water samples and milk samples.

[0098] Example 5

[0099] In this embodiment, the enrichment element from Example 1 was used to enrich and detect PFOA and PFOS in the spiked milk sample, and then the reusability was tested. The details are as follows:

[0100] Milk sample matrix solutions containing PFOA and PFOS at a concentration of 50 ng / mL were prepared. Ten extraction cycles were performed under optimal extraction conditions, and the recoveries after each cycle were assessed to evaluate the reusability of the enrichment element. The results are as follows: Figure 4 As shown, the recovery rate tends to decrease after repeated use of the enrichment element, but it remains above 80% after the 10th cycle, indicating good reusability.

[0101] Example 6

[0102] In this embodiment, the stability and batch reproducibility of the preparation process of the present invention were investigated. Enrichment elements prepared in different batches were used to extract PFOA and PFOS at a concentration of 50 ng / mL from deionized water. The stability of the enrichment elements prepared in different batches was evaluated by the average weight, average recovery rate, and relative standard deviation. Three different batches of enrichment elements were synthesized in this experiment, and three parallel experiments were conducted for each batch. The results are shown in Table 2. The weights of the three batches of enrichment elements ranged from 0.343 to 0.349 g, with a relative standard deviation of 0.33%, indicating the stability of the enrichment element preparation in different batches. The recoveries of PFOA and PFOS ranged from 85.7% to 91.8% and 82.3% to 88.7%, respectively, with relative standard deviations of 3.05% and 3.20%, respectively, indicating good batch reproducibility.

[0103] Table 2. Weight of enrichment elements and sample recovery rates among different batches.

[0104]

[0105] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0106] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing enriched elements, characterized in that, include: A non-metallic base rod is provided, the base rod being processed from wood or bamboo, the base rod having a tapered tip, and the diameter of the base rod not exceeding 15 mm, and the diameter of the tapered tip of the base rod not exceeding 0.25 mm; Graphene oxide powder is adhered to a portion of the surface of the base rod to obtain a preliminary enriched element. The enriched element precursor, template molecule, functional monomer and porogen are contacted to carry out a prepolymerization reaction in order to obtain a prepolymerized mixed system; A crosslinking agent and an initiator are added to the prepolymerized mixture, and the mixture is then subjected to a polymerization reaction under deoxygenation conditions to obtain an enriched element intermediate. The polymerization reaction is carried out at a temperature of 60-70°C for 20-30 hours. as well as The enriched element intermediate is eluted to obtain the enriched element. The template molecule is perfluorooctanoic acid (PFOA). The functional monomer is acrylamide. The crosslinking agent is ethylene glycol dimethacrylate. The molar ratio of the template molecule to the monomer and the crosslinking agent is 1:6:

12. The initiator is azobisisobutyronitrile (AIBN). The porogen is acetonitrile.

2. The method according to claim 1, characterized in that, The prepolymerization reaction is carried out under shaking conditions for 1-2 hours.

3. The method according to claim 2, characterized in that, The polymerization reaction takes 24 hours.

4. The method according to claim 1, characterized in that, Prior to the prepolymerization reaction, the process further includes: The initial sample of the element is subjected to ultrasonic cleaning with methanol and nitrogen blowing drying to obtain a dry enriched initial sample of the element.

5. The method according to claim 1, characterized in that, include: After the base rod is polished smooth, it is immersed in methanol solution for ultrasonic cleaning and then dried with nitrogen gas to obtain a pretreated base rod. A portion of the pretreated base rod is coated with a neutral silicone adhesive solution, and the graphene oxide powder is adhered to the base rod. The rod is then dried at 40-60°C, ultrasonically cleaned with methanol, and dried with nitrogen to obtain the initial enrichment element. The enriched element precursor, template molecule, and functional monomer are added to the porogen, placed on a shaker, and subjected to the prepolymerization reaction at 250-350 rpm and room temperature for 1-2 hours. The crosslinking agent and initiator are then added, nitrogen is purged to remove oxygen, and the polymerization reaction is carried out under sealed conditions at 62-68°C for 20-24 hours to obtain the enriched element semi-finished product; and The enriched element semi-finished product is eluted in a Soxhlet extractor with a methanol solution containing 8-12% acetic acid to obtain the enriched element.

6. An enrichment element, characterized in that, The enrichment element is prepared using the method for preparing enrichment elements according to any one of claims 1-5.

7. A detection device, characterized in that, Includes the enrichment element as described in claim 6.

8. A method for qualitative / quantitative detection of perfluorinated compounds, characterized in that, The method is performed using the enrichment element as described in claim 6 or the detection device as described in claim 7.

9. The method according to claim 8, characterized in that, The perfluorinated compound is perfluorooctanoic acid or perfluorooctane sulfonic acid.

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